text: DUP leader, First Minister Arlene Foster, has resisted both calls to step aside and calls to resign over the Renewable Heat Incentive (RHI) scheme.
  RHI is approximately £490m over budget.
  Sinn Féin's national chairperson Declan Kearney accused Mrs Foster and her party of "unvarnished arrogance" over the "growing political crisis".
  Writing in the the republican newspaper, An Phoblacht, Mr Kearney said: "It's increasingly obvious the DUP have lost the run of themselves within the northern political institutions."
  He repeated an earlier call by his party colleague Martin McGuinness that Mrs Foster should step aside as first minister to "allow a time-framed, comprehensive, independent investigation" into the heating scheme.
  The DUP leader set up the RHI scheme in 2012 when she was minister for enterprise, trade and investment.
  Last month she apologised for its lack of cost controls but defended her own role in the scheme.
  Sinn Féin and the DUP lead a power-sharing coalition government at Stormont, with the support of Justice Minister Claire Sugden, an independent MLA.
  However, relationships have been under increased strain as the full implications for the public purse of the botched RHI scheme have been revealed.
  Mr Kearney's article also criticised the DUP and its Communities Minister Paul Givan for last week's decision to withdraw funding for an Irish language bursary scheme.
  The Líofa (fluent) Gaeltacht bursary scheme enabled at least 100 people a year to attend summer Irish language classes in the Donegal gaeltacht.
  The funding cut was announced by Mr Givan's department two days before Christmas.
  Mr Kearney wrote: "The political process has now been dragged recklessly by the DUP, culminating with the RHI crisis towards an unprecedented tipping point.
  "Political institutions cease to have value when they do not reflect equality, mutual respect and parity of esteem, and have become detached from the lives of citizens they are meant to serve.
  "Playing fast and loose with the political process and the political institutions is unsustainable.
  "There are big decisions to make, and there is very little time."
  However, Sinn Féin was criticised by the SDLP for not supporting its call for a public inquiry into the RHI scandal.
  SDLP MLA Patsy McGlone said: "Surrendering the demand for a judge-led public inquiry is surrendering the need for transparency, accountability and consequences for the loss of hundreds of millions in public money.
  "With trust in our hard-won institutions at stake, Sinn Féin need to think very carefully on where their loyalties lie. The SDLP have been clear, only a judge-led inquiry can get to the truth of this matter."
target: Sinn Féin has accused the DUP of dragging the political process "towards an unprecedented tipping point" over the 'cash-for-ash' scandal.